A solution is prepared at that is initially in nitrous acid, a weak acid with, and in sodium nitrite. Calculate the pH of the solution. Round your answer to decimal places.

4.07

Explanation:

There is some info missing. I think this is the original question.

A solution is prepared at 25 °C that is initially 0.057 M in nitrous acid (HNO₂), a weak acid with Ka = 4.5 * 10⁻⁴, and 0.30 M in sodium nitrite (NaNO₂). Calculate the pH of the solution. Round your answer to 2 decimal places.

Nitrous acid is a weak acid and nitrite (coming from sodium nitrite) is its conjugate base. Together, the form a buffer system. We can calculate its pH using the Henderson-Hasselbach equation.

pH = pKa + log [base]/[acid]

pH = - log 4.5 * 10⁻⁴ + log 0.30/0.057

pH = 4.07